Variable antenna arrangement



VARIABLE ANTENNA ARRANGEMENT Filed June 2, 1.933

Patented Apr. 7, 1936 vUNITED VARIABILE ANTENNA ARRANGEMUENTE' tion oitGermany Application .lune 2, 1933, Serial No. @74,0% In Germany .lune 6,1932 5 illaims.

It is well known toI use in short wave transmitters of greater waverange an antenna the length of which can be varied by means of a windingdrum, in order to enable operation with a constant antenna resistance.In using a M4 antenna with coupling in the current amplitude, theantenna resistance is for instance 30 ohms. It is furthermore known touse as input supply line a line having a wave resistance equal to theantenna resistance, in'order to always obtain automatically, by avoidingspecial adapting transformers, the correct termination oi the energyline. In this case the input resistance of the line is aways equal tothe wave resistance of the line, so that the transmitter, independent ofthe Wave and supply line length, is required to only supply a constantcoupling voltage. I-Iowever, a practical difficulty is encountered bythe construction of the antenna winding drum upon which the excessantenna wire is wound. In case of greater wave resistances and energiesthe drum requires very considerable dimensions, so that its distributedcapacity against ground can no longer be neglected. Thus the capacitymust be compensated for every wave by means of special tuning measures.

In accordance with the invention this drawback is overcome in that thedrum is arranged in the interior of the supply line whereby the latteris widened so as to obtain the required space, while its wave resistanceis retained.

An embodiment of the invention is shown in the accompanying drawing byway of example.

'Ihe transmitter not shown in the drawing which is arranged in thetransmitting room S is coupled to the energy line at points k1, k2. Theline consists of two coaxially disposed pipes b and c whereby the outerpipe is ground. A vertical antenna is electrically connected to theinner pipe c, the eective length of the antenna between tension rollerr1 and insulator i can be adjusted to the respective wave length k/Ll.The tensioning of the antenna a may be accomplished for instance bymeans of a rope m passed over a roller r2 and loaded by a weight g.

In order to render the effective length of the antenna at the transitionto another frequency equal to the altered value M4 and to thuscontinuously retain the antenna resistance, the antenna wire is woundupon or unwound from a winding drum h rotatable by means of a crank 7c.

In accordance with the invention the drum h is disposed within a chamberformed by the widening c1 of the inner energy line. Corresponding withthe widening of the inner pipe, a

(Cl. Z50-33) widening b1 of the outer energy line is carried out and insuch manner that for each cross section the ratio of the diameters is somaintained that the wave resistance remains constant. The Shaft a.supporting the drum h is composed of insulating material.

It is not a necessary requirement that the inner inactive part ca of theantenna wire consists of the same material as used for the active parta. The latter consists ordinarily of material resistible againstchemical influences in particular against corrosion, such as bronze andthe like, the specific conductivity of which is relatively small, sothat the cross section oi' this antenna part becomes relatively largefor reducing the impedance. If the portion of the energy line betweendrum and antenna is longer than the largest change oi' the effectivelength oi the antenna, i. e. than the length of the wire to be woundupon or to be unwound from the winding drum, the parts of the wire whichmay eventually form portions of the eective length of the antenna a willin no case reach over the drum. In this case the wire portion passingthrough the interior space of the inner pipe c, through which currentnever flows and which only serves as a pulling wire, may be composed ofsteel or any other material, iniective for high frequency purposes, butinstead of greater mechanical strength. Thus it is made possible tosubstantially reduce the dimensions of the drum and those of the entireequipment necessary for the mounting of the drum.

I claim:

1. An antenna system comprising a vertical antenna one-quarter of thelength of the operating wave, high frequency apparatus, a pair ofconcentric inner and outer metal tubes, and a connection from said highfrequency apparatus to said inner tube, a wire disposed within saidinner tube and connected to said vertical antenna, a drum arrangementlocated at the end of said wire farthest removed from said antenna forwinding said Wire therearound for varying its effective length andsimultaneously varying the length of the vertical antenna, said wirebeing in electrical contact with said inner tube.

2. A system as dei-ined in claim l, characterized in this that saidouter metal tube is grounded.

3. An antenna system comprising a vertical antenna one-quarter of thelength of the operating wave, high frequency apparatus, a Wire extendingfrom said vertical antenna and in circuit with said high frequencyapparatus, a pair of concentric inner and outer metal tubes surroundingsaid Wire, said inner tube being in contact with said wire, a reellocated at the end of said wire farthest removed from said antenna forWinding said Wire therearound for varying its effective length andsimultaneously varying the length of the antenna, and a metal housingfor said reel, said housing connecting with said outer tube andenclosing substantially completely said reel, said housing beingconnected to ground.

4. An antenna comprising a vertical antenna one-quarter of the length ofthe operative Wave, high frequency apparatus, a pair of concentric innerand outer metal tubes, a wire disposed within and in contact with saidinner tube and connected with said antenna, and a drum arrangementlocated at the end of said Wire farthest removed from said antenna forwinding said Wire therearound for varying its effective length andsimultaneously varying the length of the antenna, said pair of metaltubes being appreciably Wider at the end of said Wire remote from saidantenna than at said antenna, said drum being located Within said innertube at its widened portion, and a connection from said high frequencyapparatus to inner tube.

5.A system in accordance with claim 4, characterized in this that theratio of the diameters of the widened portion of said pair of metalftubes is so maintained that the Wave resistance remains constant.

WERNER BUSCHBECK.

